Control for monitoring pressure in a gas blast circuit breaker



United States Patent [72] Inventor Thomas F. Clark Primary Examiner-Robert S. Macon C n Mass- .4!rorne \-Thomas F. Kirby. Robert B. Benson and Lee H. [2| 1 Appl. No. 709,096 Kaiser [22] Filed Feb. 28, 1968 [45] Patented Dec. 29, 1970 l I I [73] Assignee Allis-Chalmers Manufacturing Com any ABSTRACT: An air or gas blast circuit breaker comprises a Milwaukee, Wis. tank of pressurized air or gas to which three hollow insulating columns are connected through one-way check valves. Pressure-monitoring means are provided in the tank and in each column. With the breaker initially closed, air loss from the tank causes all the circuit breaker contacts to open simultaneously. Further loss of tank pressure causes opening of auxiliary protective devices such as disconnect switches. After a time [54] CONTROL FOR MONITORING PRESSURE IN A lapseduring which air column pressure intentionally falls, all GAS BLAST CIRCUIT BREAKER circuit-breaker contacts reclose. With the breaker initially 10 Claims, 1 Drawing Fig closed. a slow loss of gas pressure from one or more columns causes all circuit-breaker contacts to open simultaneously and [52] [1.8. CI 200/148, a the auxiliary protective devices to open with the breaker 200/82 initially closed, a rapid loss of gas pressure from one or more [5]] lift. Cl ..H0lh 33/83 columns Causes a" circuit breaker contacts to remain closed [50] Fleld olSearch 200/148, and the auxiliary protective devices remain closed w the 1484' 148-1821 breaker initially open, air loss from the tank allows the breaker contacts to remain open but causes the auxiliary pro- [561 References cued tective devices to open. With the breaker initially open, air UNITED STATES PATENTS loss from one or more columns causes all the circuit breaker 3,083,277 3/1963 Tsutsyietal. 200/82(.l) contacts to close simultaneously but the auxiliary protective 3,248,507 4/l966 Holzinger 200/148 devices do not open.

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". Dl'S/fl/ATES SWITCH CONTACTS/0P6) DESIGNATES SWITCH CONTACTS 640560) CONTROL FOR MONITORING PRESSURE IN A GAS BLAST CIRCUIT BREAKER SUMMARY OF THE INVENTION This invention relates to a control system for an air blast or gas blast-type electric circuit breaker. More particularly, it relates to a control system for monitoring air or gas pressure (hereinafter called air pressure) in various parts of of the circuit breaker and for providing an appropriate response in the event of pressure loss.

In one type of air blast or gas blast circuit breakers (hereinafter called air blast circuit breakers) there is provided a tank or reservoir of pressurized air which is connected to a plurality (usually three or more) hollow insulating columns. Each column supports and is in communication with at least one chamber in which one or more pairs of relatively movable circuit-breaker contacts are located. Output terminals 64 and 66 are connected to a coil 65. In some versions of a circuit breaker of the foregoing type a contact control tube is associated with each insulating column for admitting the pressurized air from the column to cause opening of the circuit breaker contacts located in each associated chamber. A control valve and a blast valve are located in the contact control tube circuit. Operation of each control valve causes operation of the blast valve and consequent operation of the pair of associated circuit-breaker contacts. Pressurized air in each columnand its associated chamber provide some of the necessary electrical insulating function for the circuit breaker. Maintenance of air pressure in the tank'is required to enable the circuit-breaker contacts to be opened and closed as required. Maintenance of air pressure in the columns and chambers, and availability of air pressure to the contact control tube is also required for operational purposes and for adequate dielectric purposes.

Heretofore, control systems were provided which were responsive to overall system pressure and caused all the circuit-breaker contacts to close if air pressure failed anywhere are provided in the tank and in each column downstream of the check valve. With the breaker initially closed, air loss from the tank'causes all the circuit-breaker contacts to open simultaneously. Further loss of tank pressure causes opening of auxiliary protective devices such as disconnect switches. After a time lapse during which air column pressure intentionally falls. all circuit-breaker contacts reclose, with the breaker initially closed. a slow loss of gas pressure from one or more columns causes all circuit-breaker contacts to open simultaneously and all the auxiliary protective devices to open. With the breaker initially closed, a rapid loss of gas pressure from one or more columns causes all circuit-breaker contacts to remain closed and the auxiliary protective devicesremain closed. With the breaker initially open, air loss from the tank allows the breaker contacts to remain open but causes the auxiliary protective devices to open. With the breaker initially open, air loss from one or more columns causes all the circuit breaker contacts to close simultaneously but the auxiliary protective devices do not open.

OBJECTS It is an object of the present invention to provide an improved control system for an air blast circuit breaker which monitors air pressure in various parts of the circuit breaker which discriminates betweentotal and partial loss of insulating capability caused by pressure loss. and'which effects uniform reaction in circuit-breaker contact operation in response to pressure loss.

Another object is to provide an improved control system of the aforesaid character which is relatively economical to manufacture and reliable in operation.

Other objects and advantages will hereinafter appear.

DESCRIPTION OF THE DRAWING DETAILED DESCRIPTION OF THE INVENTION Referring to the drawing, there is shown an air blast circuit breaker and control system therefor in accordance with the present invention. The circuit breaker comprises a compressed air tankor reservoir 10 which is adapted to be supplied with compressed air through an inlet 12 from a suitable source. Three insulated hollow tubular support columns l4a. 14b and 140 are connected to tank 10 and the columns are rovided with one-way check valves 16a, 16b and 160 respectively, which permit air to flow from the tank into each column but not in the reverse direction. The columns 14a, 14b and 14c are provided at their top ends with chambers 18a, 18b and 18c, respectively, in which relatively movable circuitbreaker contacts 20a, 20b and 20c, respectively, (shown schematically) are located. Within the columns 14a, 14b and Me, there are a located control tubes 22a, 22b and 22c, respectively, which are associated with control valves 24a, 24b and 246. respectively, and with blast valves 26a, 26b and 26c, respectively.

It is to be understood that, normally high pressure, for example on the order of 400 p.s.i., exists in tank 10, in columns 14a, 14b andl4c, and in chambers 18a, 18b and 18c. Opening of a control vvalve permits pressurized air in the associated column (downstream of the check valve) to enter the control tube an effect opening of the blast valve thereby causing the associated circuit-breaker contacts to open. Closure of a control valve causes closure of the associated circuit-breaker contacts. Y

The columns 14a, 14b and Me are provided with suitable pressure responsive devices 28a, 28b and 280, respectively, which monitor pressure conditions within ,their respective columns and chambers, downstream ofthe check valves. Tank 10 is also provided with suitable pressure-responsive devices 30a and 30b which monitor pressure conditions therewithin.

The electrical control for a control system in accordance with the present invention is arranged as follows.

There is provided an electrical power source. preferably direct current, which comprises a pair of terminals 32 and 34. A closing coil 36 is connected across terminals 32 and 34 in series with a pressure-responsive switch 38 and a manually or electrically operable closing switch 40. Closing coil 36 is connected by suitable means 42 to each control valve 24a, 24b

' and 240 to effect closing thereof. Pressure-responsive switch 38 is connected by suitable means 44 to pressure responsive device 30a in tank 10. v

A tripping (or opening) coil 46 is connected across terminals 32 and 34 in series with a switch 48 which responds to breaker contact position (i.e., when the breaker contacts 20a, 20b and 200 are are closed switch 48 is closed and vice versa) in series with a pressure-responsive. switch 50, and a manually or electrically operable tripping (opening) switch 52. Tripping coil 46 is connected by suitable means 54 to each control valve 24a, 24b and 24c to effect opening thereof.

Three pressure-responsive switches 56a, 56b and 560 are connected in parallel with each other across the terminals 32 and 34 in series with closing coil 36. The pressure-responsive switches 56a, 56b and 560 are connected by suitable means 58a, 58b and 58c, respectively, to the pressure-responsive devices 28a, 28b and 28c, respectively.

Three pressure-responsive switches 60a, 60b and 60c are connected in series with each other across the terminals 32 and 34 in series with a pressure-responsive switch 62, switch 48 and tripping coil 46. The pressure responsive switches 60a, 60b and 600 are connected by the means 58a, 58b 58c, respectively, to the pressure-responsive devices 28a, 28b and 28c, respectively, and are understood to operate simultaneously (but reversely with the pressure switches 56a, 56b and 560).

A pair of output of terminals 64 and 66 are connected across the terminals 32 and 34 in series with a switch 68 (which is understood to open when the circuit-breaker contacts 20a, 20b and 200 close an vice versa) and a pressureresponsive switch 70 which is connected by suitable means 44 to pressure-responsive device 30a in tank 10. A circuit z breaker of the same general type as, that just referred to is shown in US. Pat. No. 3,248,507 issued Apr. 26, l966 to K. Holzinger for Pressurized Gas Operated Circuit Breaker with Load lnterrupter and lsolator Contact Means." An output (or chambers 18a, 18b arid 18c) downstream of the check valves 16a, 16b and 16c. One or more of the pressure-responsive devices 28a, 28b and 28c will respond to effect closing of the associated pressure switches 56a. 56b and 560 (and opening of the associated pressure switches 60a, 60b and 606).:

However, trip coil 46, will not be energized even though pressure switch 50 opens and pressure switch 6'2 closes. Auxiliary switch 68 remains open and no signal appears across terminals 64 and 66 to effect opening of an'y auxiliary disconnect devices (not shown). However, a slow loss of gas pressure from one or more columns allows the circuit breaker contacts to open and a signal to appear across the-terminals 64 and 66 to open the .disconnect switches (not shown BREAKER OPEN AlR LOSS FROM TANK 1 and 20c remain open and a signal appears across the terminals signal from terminals 64 and 66 is adapted to effect energization of coil 65 and opening of protective devices. such as isolator and disconnect switches 21a, 21b and 210 which would be in circuit with the circuit-breaker contacts 20a, 20b and 20c The control system hereinbefore described operates as follows.

BREAKER CLOSED AIR LOSS FROM TANK energized through the switches 48, 62 and 60a, 60b and 600.

' Energization of trip coil 46 causes opening of the control valves 24a, 24b and 24c, openingof the blast valves 26a,26b and 260, respectively, and opening of the circuit-breaker contacts 20a, 20b and 200, respectively. As the circuit-breaker contacts 20a, 20b and 200 open. the auxiliary switch 68 closes and-the auxiliary switch 48 opens to deenergize trip coil 46.

As the pressure in tank l-drops still lower, the pressure-.

responsive device 30a in tank (which is set to respond to a lower predetermined level than pressure-responsive device 30b) responds to effect closing of pressure switch 70 (and opening of pressure switch 700) thereby causing an electrical signal to appear across the terminals 64 and 66 which is available to open auxiliary switching devices such as disconnect switches (not shown) or the like. After a further period of time. for example about one hour. further loss of pressure causes operation of one or more of the pressure-responsive devices 28a, 28b and 280, which monitor pressure in columns 14a, 14b and Me, respectively, to cause closing of its associated pressure switch 56a, 56b or 560 (and opening of pressure switches 60a. 60b or 600) to effect energization of closing coil 36. It is to be understood that this loss of pressure in one or more of the columns 14a, 1412 or 14c (and the associated chambers 18a, 18b or 18c) is intentional and-due to natural bleeding or breathing of air therefrom. Energization of closing .coil36 causes closing of the control valves 24a, 24b and 24c and. consequent reclosing of the circuit-breaker contacts a,

20b and 201'.

BREAKER CLOSED AlR LOSS FROM COLUMN Assume that the circuit breaker is closed. that tank 10 and the columns and chambers are pressurized and that a rapid air lass occurs from one or more ol'the columns 14a, 14b and 14c closing of pressure switch 62 thereby causing trip coil 46 to be 64 and 66 to effect opening of any auxiliary disconnect devices(notshown).

BREAKER OPEN AIR LOSS FROM COLUMN 7 sure switches 56a, 56b or 56c toeffect operation of the control valves 24a, 24b and 24c and the blast valves 26a, 26b and 26: and closing of the circuit-breaker contacts 20a, 20b and 200.

As the circuit-breaker closes, auxiliary switch 68 opens thereby preventing a signal across the terminals 64 and 66 and preventing opening of the auxiliary disconnect devices (not .shown). i

lclaim: Y i

1. ln a control system for a gas blast electric circuit breaker; a reservoir for pressurized-gas;

a plurality of hollow insulating columns for receiving gas from said reservoir; 3 an individual check valve for each column to permit gas flow from said reservoir into each column but to prevent gas flow in thereverse direction; at least one pair of separable circuit-breaker contacts associated with each column;

a control valve for controlling operation'of each pair of circuit-breaker contacts; 5 each of said control valves controlling gas flow from its respective column downstream of the check valve for that column; first pressure-responsive means for monitoring gas pressure in'said tank and for operating all said control valves to effect simultaneous circuit-breaker contact operation; and

second pressurefres ponsive means for monitoring gas pressure in each column individually and for operating all said control valves to effect simultaneous circuit-breaker contact operation. 7

2. A control system according to claim 1 including auxiliary protective devices in circuit with said circuit-breaker contacts, said devices being operated by said first and second pressureresponsive means.

3. A control system according to claim I wherein said first means responds to a predetermined pressure loss in said tank to effect opening of all circuit-breaker contacts simultaneously.

4 A control system according to claim 1 wherein said second means responds to a predetermined pressure loss in at least one of said columns to effect opening of all circuitbreaker contacts simultaneously. g

5. A control system according to claim 2 wherein said first means responds to a predetermined pressure loss in said tank to effect opening of all circuit-breaker contacts simultaneously and to further respond to a further loss of pressure to effect opening of said auxiliary protective devices.

6. A control system according to claim 5 wherein said second means responds to a predetermined pressure loss in at least one of said columns subsequent to the said further loss of pressure in said tank to effect reclosing of all of said circuitbreaker contacts simultaneously.

7. A control system according to claim 2 wherein saidsecond responds to a predetermined pressure loss in at least one of said columns to cause all circuit-breaker contacts to open simultaneously and to effect opening of said auxiliary protective devices.

8. A control system according to claim 2 wherein said second means responds to a predetermined pressure loss in at least one of said columns to cause all circuit-breaker contacts to remain closed and to cause said auxiliary protective devices to remain closed.

9. A control system according to claim 2 wherein said first means responds to a predetermined pressure loss in said tank to cause all circuit-breaker contacts to remain open and causes said auxiliary protective devices to open.

10. A control system according to claim 2 wherein said second means responds to a predetermined pressure loss in at least one column to effect simultaneous closing ofall said circuit-breaker contacts and causes said auxiliary protective devices to remain closed. 

